Integral lash adjuster



Sept. 17, 1968 R. c. RONZI 3,401,677

INTEGRAL LASH ADJUSTER Filed Aug. 29, 1 967 2 Sheets-Sheet 1 F/GZ ltd 4K0 C. rPO/VZ/ INVENTOR.

ATTORNEYS p 1968 R. c. RONZI 3,401,677

INTEGRAL LASH ADJUSTER Filed Aug. 29, 1967 2 Sheets-Sheet 2 n N \9 Q N Q F/& 2

RICH/4RD C. AO/VZ/ INVENTOR.

m BY 2 United States Patent m 3,401,677 INTEGRAL LASH ADJUSTER Richard C. Ronzi, Southfield, Mich., assignor to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed Aug. 29, 1967, Ser. No. 664,114 9 Claims. (Cl. 123-90) ABSTRACT OF THE DISCLOSURE A hydraulic lash adjuster is built into the support shaft for the rocker arm of a reciprocating engine valve train. A chamber is formed in the support shaft and connected to the engine oil supply. Mounted in the chamber is a piston subject to oil pressure on one side and having an inclined surface on the other side. The inclined surface bears on a correspondingly inclined surface of a member projecting down through an opening in the wall of the shaft, and this member bears on the lower inside surface of the bore in the rocker arm. Engine oil pressure positions the piston, the piston acts through the inclined surfaces to position the member projecting through the opening in the shaft wall, and the member in turn positions the rocker arm to eliminate lash existing in the valve train.

Summary of the invention Commercialized reciprocating engines having overhead camshafts and overhead valves generally have not had hydraulic lash adjusters associated with the valve trains because of space limitations. The hydraulic lash adjuster usually proposed for such valve trains were modified versions of the lash adjuster used in engines having the camshaft in the engine block. Typically, these adjusters were mounted above the rocker arm where they were anchored to the rocker arm mounting stud or a reaction bar fixed with respect to the engine head. Obviously, such construe tions increased engine size considerably. Furthermore, passages or external tubing were necessary to conduct engine oil under pressure to the adjuster, thereby increasing component and assembly costs.

This invention provides a lash adjuster integral with a support shaft that acts on the rocker arm and can be used to eliminate lash in any mechanism for converting rotational motion of the camshaft into reciprocating motion of a reciprocating member without substanitally increasing package size. The adjuster preferably is hydraulically operated and is particularly useful in the valve train of reciprocating engines having an overhead camshaft and overhead valves because of the crucial space limitations therein. In a mechanism for converting rotating motion of the camshaft into reciprocating motion of a reciprocating member by means of a rocker arm, the hydraulic lash adjuster of this invention comprises a support shaft for the rocker arm containing a chamber for hydraulic fluid and having an opening in a wall, an inlet for admitting hydraulic fluid to the chamber, a piston mounted in the chamber between the inlet and the opening, and a member located in the opening for movement at an angle to the axis of the support shaft. Both the piston and the member have a surface angled relative to the axis of the support shaft and these surfaces are in sliding contact with each other. The rocker arm is located on the support shaft in contact with the member so the position of the member determines the radial location of the rocker arm relative to the support shaft.

Passages communicate engine oil under pressure to the chamber, and a check valve positioned conveniently in the mouth of the passage prevents oil from flowing out of the chamber when loads are applied from the rocker arm via the wedging action of the member located in the open- 3,401,677 Patented Sept. 17, 1968 ing to the piston. The oil trapped in the chamber retards the collapse of the adjuster so the motion of the camshaft is translated through the rocker arm to operate the valve. When the loads on the rocker arm are reduced, oil flows into or out of the chamber to compensate for lash changes. Brief description of the drawings FIGURE 1 is a side view of an engine head having an overhead camshaft and an overhead valve showing a support shaft containing the lash adjuster of this invention located between the camshaft and the valve stem. FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1 showing the structural relationship of the components making up the lash adjuster.

Detailed description Referring to FIGURE 1, the engine head is represented generally by the numeral 10. A camshaft 12 is rotatably mounted on one side of the head and a reciprocating poppet type valve having a valve stem 14 is mounted on the other side. A conventional valve spring 16 is mounted concentrically around valve stem 14 and bears on a retainer 18 that is locked to the valve stem by a locking means 20.

Located between the camshaft and the valve is a support post 22. Post 22 carries a support shaft 24 for the rocker arm 26. The end of the support shaft 24 is closed by a plug 28.

Turning to FIGURE 2, shaft 24 is fastened to post 22 by a bolt 30 passing through the approximate center of the shaft. Chambers 32 and 32 are formed in each end of shaft 24 and the inner ends of the chambers communicate with a passage 34 connected to the pressure side of the engine oil pump (not shown). An annular groove 35 conducts oil around bolt 30. The openings of passage 34 into chambers 32 and 32 are flared as at 36 and 36 and ball checks 38 and 38' are located in the respective flared portions, which form valve seats therefor. Retainers 40 and 40' fit into the inner ends of chambers 32 and 32' to hold the ball checks in the immediate area of the flared portions.

Pistons 42 and 42' are located slidably in the respective chamber. Each piston has an inner surface 44 and 44' exposed to oil pressure and a surface 46 and 46 angled relative to the axis of shaft 24 at the opposite side. Openings 48 and 48' are formed in the wall of shaft 24 that faces engine head 10 outboard of the respective piston and a follower member 50, 50' fits slidably in the respective opening. The inner surfaces 52 and 52' of followers members 50 and 50 also are angled relative to the axis of support shaft 24 with the angles thereof corresponding to the angles of surfaces 46 and 46'. Surface 52 slidably contacts surface 46 and surface 52' slidably contacts surface 46'. The lower surfaces 54 and 54 of members 50 and 50 are located a short distance outside of support shaft 24.

A compressive spring 56 is located between surface 44 and retainer 40 and a compressive spring 56 is located between surface 44' and retainer 40. Plug 28 and a corresponding plug 28' close the ends of respective chambers 32 and 32'. Outwardly facing abutments 58 and 58 are formed on the exterior surfaces of shaft 24 near the central portion thereof. Washers 60 and 60' are positioned against the respective abutment and rocker arm 26 and its corresponding rocker arm 26 are positioned against the respective washer. The bores in rocker arms 26 and 26' are slightly larger than the outside diameter of shaft 24 and the lower inner surface of each bore bears against respective surface 54 and 54'. Outboard of the rocker arms is another washer 62, 62' which is held in place by a retainer 64, 64'. The retainers in turn are held in position by cotter pins 66, 66 that pass through appropriate holes in the shaft wall and plug.

Operation Rotation of camshaft 12 acts trough rocker arms 26 and 26 to produce reciprocating motion of the valves associated with valve stem 14 and its corresponding stem 14' in the conventional manner, with the rocker arms pivoting about shaft 24. Because of manufacturing tolerances, thermal expansion, etc., some looseness or lash exists between the camshaft, rocker arms and valve stems. Ordinarily, the lash is less than several thousandths of an inch but even this small amount is sufficient to cause noisiness and excessive wear and interfere with engine operation.

The lash adjuster eliminates the lash in the following manner. When the valve is closed, that is, when the nose of the camshaft is out of touch with the rocker arm, engine oil under pressure in passage 34 unseats ball checks 38 and 38 and enters chambers 32 and 32' through appropriate openings in retainers 40 and 40. The oil exerts hydraulic pressure against surfaces 44 and 44', thereby urging pistons 42 and 42 axially outward. Pistons 42 and 42 in turn act through surfaces 46 and 46' to urge members 50 and 50' radially downward. Members 50 and 50' act on the loaded sides, which in this case are the lower portions, of rocker arms 26 and 26' to urge the rocker arms downward and thereby close the gap existing in the valve train. In accordance with conventional lash adjuster operation, the hydraulic pressure is insuflicient to overcome the force of the valve springs.

When the nose of the camshaft rotates into contact with rocker arm 26, rocker arm 26 pivots about the shaft to begin the reciprocating motion of the valve. The increased force on the rocker arm urges the rocker arm upward and is transmitted back through member 50, surfaces 52 and 46 to piston 42. Piston 42 increases the pressure in chamber 32 and the increased pressure seats ball check 38 to prevent oil from flowing out of the chamber and thereby collapsing the adjuster. Continued rotation of the camshaft acts through the rocker arm to reciprocate the valve.

Suflicient clearance exists between piston 42, member 50 and chamber 32 to permit leakage of small amounts of oil out of chamber 32. This leakage prevents the adjuster from becoming overadjusted which would prevent the valve 14 from seating when the nose of the camshaft is out of touch with the rocker arm. Additionally, the leakage provides lubricating oil to areas having relative motion such as surfaces 46, 52, and 54. After the valve has opened and closed, engine oil under pressure again is metered into chamber 32 to compensate for the leakage and for any increases in lash. A similar mode of operation adjusts rocker arm 26 for any lash existing in that valve train.

A passage can be formed in piston 42 to positively conduct lubricating oil from chamber 32 to surfaces 46 and 52. Any resilient or adjustable means can be used in place of the hydraulic fluid to position the piston. Relative motion between rocker arm 26 and member 50 can be eliminated and surfaces 46 and 52 can be made planoconvex and lano-concave, respectively, so the rocking motion of the rocker arm produces relative motion at surfaces 46 and 52 instead of at surface 54. Surfaces 46 and 52 preferably are inclined about 45 relative to the axis of shaft 24 but other angles can be used to optimize the lash adjuster to particular valve train characteristics. Thus, angles less than 45 decrease the proportion of the hydraulic force transmitted to the rocker arm while angles greater than 45 increase the proportion. Note that the opposite is true for collapsing forces transmitted back through member 50 from the rocker arm.

Thus this invention provides a lash adjuster for an overhead camshaft engine that does not require significant in- 4 creases in engine size. The adjuster can be used to take up the looseness of any pivoting member mounted on a support shaft, or it can be used to hold a member mounted on the support shaft in contact with another element with a resilient force.

What is claimed is: I I

1. In a mechanism for converting rotating motion of a camshaft into reciprocating motion of a reciprocating member by means of a rocker arm, a hydraulic lash adjuster comprising a support shaft for the rocker arm, said support shaft containing a chamber for hydraulic fluid and having an opening in a wall,

inlet means for admitting hydraulic fluid to said chamher,

a piston mounted in said chamber between said inlet means and said opening, said piston having a surface angled relative to the axis of the support shaft, and

a member located in said opening for movement at an angle to the axis of the support shaft, said member having a surface angled relative to said axis in contact with the angled surface of the piston so the position of said member in said opening is determined by the pressure of the hydraulic fluid on the piston, said rocker arm being located on said support shaft in contact with said member so the position of said member determines the location of said rocker arm.

2. The mechanism of claim 1 in which the reciprocating member is a poppet type valve of a reciprocating internal combustion engine.

3. The mechanism of claim 2 in which the camshaft is an overhead camshaft and the valve is an overhead valve.

4. The mechanism of claim 3 in which the support shaft is fastened to the engine head at the approximate center of the support shaft, and the support shaft contains one of said chambers on each side of the fastening.

5. The mechanism of claim 4 comprising passage means for supplying engine lubricating oil under pressure to said chambers.

6. The mechanism of claim 1 in which the support shaft is fastened to the engine at the approximate center of the support shaft, and the support shaft contains one of said chambers on each side of the fastening.

7. A lash adjuster comprising a support shaft having a chamber therein,

a first member mounted in said chamber for movement along the axis of the support shaft,

means for positioning said first member,

a second member mounted in wedging contact with said first member, said second member being movable at an angle to the axis of the support shaft, and

a pivoting member mounted on said support shaft and contacted by said second member so any looseness in the mounting of the pivoting member is taken up by movement of the first member.

8. The lash adjuster of claim 7 in which the second member projects through an opening in the side of the support shaft facing the loaded side of the pivoted mem ber.

9. The lash adjuster of claim 8 in which hydraulic means are used to position the first member.

References Cited UNITED STATES PATENTS 1,872,083 8/1932 Hutchison l23--90 2,053,743 9/1936 Russell 12390 2,845,053 7/1958 Humphreys 123-90 3,087,476 4/1963 Fairchild 12390 AL LAWRENCE SMITH, Primary Examiner. 

